Show Notes
In this episode, host Kumar speaks with Joshua Elliott, Chief Scientist at Renaissance Philanthropy and a former prolific DARPA program officer. Joshua brings deep personal passion to climate work and is a constant source of ideas who also sharpens others’ program designs.
Joshua discusses the Advance Research for Climate Emergencies (ARC) Initiative at Renaissance Philanthropy, through which the team identifies experts and ideas, incubates them from small seed grants into fully staffed build-grant programs, and launches them.
Joshua traces his ambitious, technically rigorous approach to his years at DARPA, which gave him permission to chase ideas others called impossible. Widely sought out for mentorship, he talks about the Climate Emergency Forum and issues an appeal to scientists and nonprofit leaders.
*Tacit Knowledge *
Hosted by Kumar Garg
Presented by Renaissance Philanthropy
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Produced by All Together Now
FOLLOW JOSHUA
LinkedIn: https://www.linkedin.com/in/joshuawrightelliott/
Substack (The ARC): https://arcinit.substack.com/
KEY QUESTIONS & TAKEAWAYS
What is the "Sulfur Tracking Program" trying to figure out?
An in-development ARC initiative (still under a stealth name) aimed at launching small satellites and balloon-based sensors to resolve one of climate science's biggest open questions: how much of the Earth's declining reflectivity is due to falling aerosol pollution versus a warming-driven feedback loop that's itself reducing cloud cover.
Why might Earth's declining reflectivity be as big a driver of warming as greenhouse gases?
NASA's CERES satellite data suggests the planet has lost enough reflectivity since 2000 to contribute roughly 2.7 W/m² of climate forcing — a number comparable to the instantaneous forcing from all greenhouse gases emitted since the Industrial Revolution. That comparison is still being finalized in peer review, but it points to a second, under-discussed pillar of climate change alongside emissions.
Why has industrial pollution been masking warming, and what happens as it's cleaned up?
Burning fossil fuels releases sulfur dioxide and other aerosols that seed brighter, more reflective clouds. That pollution layer is estimated to be offsetting about half a degree of global warming — meaning, as Joshua puts it, we're already living in a "near two-degree world" that's been masked by the dirtiest possible form of accidental geoengineering. As pollution controls reduce aerosol emissions, that masking effect declines too.
What's driving the rest of the loss in Arctic ice and cloud cover?
About 30% of lost reflectivity comes from vanishing ice and snow cover (largely Arctic sea ice, mountain glaciers). The remaining majority comes from changes in cloud cover — and current observational and modeling capabilities can't yet disentangle how much of that is falling aerosol pollution versus a self-reinforcing, warming-induced feedback loop.
Why do the most accurate climate models predict more warming, not less?
A recent study comparing the ~40 global climate models in the CMIP archive found that the models which most accurately reproduce observed changes in reflectivity and Earth's energy imbalance also tend to show 1.5–2x higher climate sensitivity than the model average. If those more accurate models are right, a projected 2.5–3°C future could actually be closer to 4.5–5°C.
What is the Heilmeier Catechism, and how does Joshua use it?
A set of pressure-testing questions developed by former DARPA director George Heilmeier to evaluate research proposals. Joshua distills it into four core questions he uses as a first-pass filter for any ambitious idea: what are you trying to do, who's doing it now and what's wrong with that, what's your big insight, and who cares.
What are the ARC Initiative and BiTS?
ARC (Advanced Research for Climate Emergencies) is Renaissance Philanthropy's "nonprofit venture studio" model for finding experts and ideas and building them
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